On 8/2/2019 5:12 PM, Jason Resch wrote:
On Fri, Aug 2, 2019 at 6:51 PM 'Brent Meeker' via Everything List <[email protected] <mailto:[email protected]>> wrote:On 8/2/2019 4:36 PM, Jason Resch wrote:On Fri, Aug 2, 2019 at 5:18 PM 'Brent Meeker' via Everything List <[email protected] <mailto:[email protected]>> wrote: On 8/2/2019 1:41 PM, Jason Resch wrote:On Fri, Aug 2, 2019 at 3:31 PM 'Brent Meeker' via Everything List <[email protected] <mailto:[email protected]>> wrote: On 8/2/2019 1:19 PM, Jason Resch wrote:On Fri, Aug 2, 2019 at 3:17 PM 'Brent Meeker' via Everything List <[email protected] <mailto:[email protected]>> wrote: On 8/2/2019 12:53 PM, Jason Resch wrote:On Fri, Aug 2, 2019 at 1:25 PM 'Brent Meeker' via Everything List <[email protected] <mailto:[email protected]>> wrote: On 8/2/2019 10:42 AM, Jason Resch wrote:Quantum computers work by interference of quits, and such interference can only take place in one world -- different worlds are orthogonal. The fact that one can analyse a quantum computer in a particular basis which can be represented as a series of parallel computations does not mean that this is actually what happens. Heuristic constructs seldom correspond to reality. None of this comes anywhere close to addressing my question. Well, you have either not understood the question, or my answer to it. I asked where those 10^1000 intermediate computation states are realized, and your reply was a basic description of how quantum computers use qubits and interference. You said this all takes place in one world, but the total information content and computational capacity of the observable universe about 800 orders of magnitude less than 10^1000. You then added a sentence that suggested the intermediate computational states perhaps don't exist, but then how does the correct answer get into the output bits when we read it? David Deutsch said he has never seen a sensible answer to the question of how quantum computers work from the context of any single-universe interpretation. Do you think your answer would satisfy him?All those "intermediate computation states" are so "numerous" because the state is being expressed as a superposition of qubit basis states. From another viewpoint the state is just a single ray in Hilbert space that happens to not be orthogonal to any of those bases So in your view, are they real?What "they"? There's only a single state. It's like saying there are infinitely many tones in a square wave...just because you represented it as a Fourier series. The are 2^1e4 potential measurement results, depending on what you choose to measure...but that's true in the classical case too. Do you agree the final states you measured were caused by the intermediate states of the computation? How many intermediate states of the computation are there?One. It's a unitary evolution of the input state. We were speaking of computational states. Are you saying there is only one computation state involved in Shor's algorithm? What causes the interference necessary to yield the correct answer, if not these numerous computational states?The interference is in the measurement which Deutsch would say projects out onto one of the multiple worlds...the non-unitary step. Does anyone claim interference happens during the measurement? In the double slit experiment the interference happens when the two photons overlap in their position, not when they strike the photographic plate.You write as though they were classical particles. The wave function reaches the photographic plate and then there is an interaction which is greater or lesser depending on the interference pattern over the plate.To say interference happens at the time of measurement may be satisfactory for making predictions, but it is completely unsatisfactory for explanations. It is a way of stuffing the intermediate computations under the rug and pretending they were never there. What of the conscious states implied by the computations of an AI on a quantum computer? "Forget about them, they never really existed."Deutsch says as much in his introduction to Fabric of Reality when speaking of shadow selves and shadow photons.You can stop quoting Deutsch. I think he's just a MWI envangelist. Okay. It was only in response your mention of Deutsch.
You cited him first: "David Deutsch said he has never seen a sensible answer to the question of how quantum computers work from the context of any single-universe interpretation."
I thought you were suggesting Deutsch believed interference happens during measurement.
Wherever it happens, it's one world. Worlds are things things that are orthogonal on to one another so that's why they're separate. I don't know what Deutsch believes.
In any case, you have still managed to avoid the question of the reality of the 10^1000 intermediate computational states. I won't press for an answer if you don't have one.I already gave the answer. There is only one intermediate state. It just happens to have lots of components in the basis you used to express it.And each of those components represents a trace of a computation performed on one of the many possible values of the input qubits, do they not?
That's one way of representing them. Just as citing the Fourier components of a firecracker going off shows the many components of the sound.
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